Brisbane Roar are bona fide A-League title favourites after thumping second-placed Adelaide United in the top-of-the-table clash at Suncorp Stadium on Saturday night.

Despite playing a man down for almost 40 minutes after first half hero Reinaldo was sent off, Brisbane cut a swathe through United's defence to win 4-0 in front of 13,248 spectators.

The victory means Brisbane sit four points, and more than one win, clear of United who have a game in hand.

The Roar were leading 1-0 when their gun striker Reinaldo received his second yellow card in the 54th minute.

His departure could easily have destroyed morale and forced the Roar to shut down the game to preserve their lead.

Instead, they went on the offensive, scoring three goals in 11 minutes to completely rattle United's defence and stamp themselves as title favourites.

Within two minutes of Reinaldo being benched, Matthew Smith scored from directly in front after a well weighted cross from Erik Paartalu.

Then lively forward Kosta Barbarouses found the net in the 62nd and 67th minutes to put the result well beyond doubt.

His second goal was from a driving right-foot shot from some 25m in open territory after running on to a Luke DeVere pass.

Reinaldo, who kicked the opening goal in the 43rd minute, drew two yellow cards for undisciplined acts after taking off his shirt in his goal celebration and then later mouthing off at the referee.

His absence, though, had more of an influence on the outcome than his presence.

The Roar had plenty of chances in the first half to be more than 1-0 up after skipper Matt McKay had five clear scoring attempts in eight minutes.

Yet McKay could only tease, and not please, Roar supporters.

United started well and looked the most likely to open the scoring following two superb crosses from Lucas Pantelis inside the opening 20 minutes.

His passes set up Iain Ramsay and Fabian Barbiero, but both of their attempts, which came within the space of four minutes, sailed over the cross bar.

Roar coach Ange Postecoglou said even he was surprised by the way his reacted so positively to Reinaldo being red-carded and being reduced to 10 men.

"It was a fantastic response," Postecoglou said.

"It was like we lifted another gear.

"I thought we were untouchable there for 10 or 15 minutes even with 10 men."

Adelaide coach Rini Coolen said Roar were clearly the best side in the competition and his team had nothing to be ashamed of given they are missing a couple of key players.

"They were too good for us," Coolen said.

"They're definitely the best team in the league. They are too good for all the teams.

"Our full squad has to be available to beat them."